Timothy Williamson gives an original and provocative treatment of deep metaphysical questions about existence, contingency, and change, using the latest resources of quantified modal logic. Contrary to the widespread assumption that logic and metaphysics are disjoint, he argues that modal logic provides a structural core for metaphysics.

Timothy Williamson is one of the most influential living philosophers working in the areas of logic and metaphysics. His work in these areas has been particularly influential in shaping debates about metaphysical modality, which is the topic of his recent provocative and closely-argued book Modal Logic as Metaphysics (2013). This book comprises ten essays by metaphysicians and logicians responding to Williamson’s work on metaphysical modality, as well as replies by Williamson to each essay. In addition, it contains an original essay by Williamson, ‘Modal science,’ concerning the role of modal claims in natural science. This book was originally published as a special issue of the Canadian Journal of Philosophy.

The philosophy of modality investigates necessity and possibility, and related notions—are they objective features of mind-independent reality? If so, are they irreducible, or can modal facts be explained in other terms? This volume presents new work on modality by established leaders in the field and by up-and-coming philosophers. Between them, the papers address fundamental questions concerning realism and anti-realism about modality, the nature and basis of facts about what is possible and what is necessary, the nature of modal knowledge, modal logic and its relations to necessary existence and to counterfactual reasoning. The general introduction locates the individual contributions in the wider context of the contemporary discussion of the metaphysics and epistemology of modality.

The only book to investigate the parallel between what happens at other times and what happens in other possible worlds.

The Actual and the Possible presents new essays by leading specialists on modality and the metaphysics of modality in the history of modern philosophy from the seventeenth to the twentieth centuries. It revisits key moments in the history of modern modal doctrines, and illuminates lesser-known moments of that history. The ultimate purpose of this historical approach is to contextualise and even to offer some alternatives to dominant positions within the contemporary philosophy of modality. Hence the volume contains not only new scholarship on the early-modern doctrines of Baruch Spinoza, G. W. F. Leibniz, Christian Wolff and Immanuel Kant, but also work relating to less familiar nineteenth-century thinkers such as Alexius Meinong and Jan Lukasiewicz, together with essays on celebrated nineteenth- and twentieth-century thinkers such as G. W. F. Hegel, Martin Heidegger and Bertrand Russell, whose modal doctrines have not previously garnered the attention they deserve. The volume thus covers a variety of traditions, and its historical range extends to the end of the twentieth century, addressing the legacy of W. V. Quine's critique of modality within recent analytic philosophy.

Modal logic, developed as an extension of classical propositional logic and first-order quantification theory, integrates the notions of possibility and necessity and necessary implication. Arguments whose understanding depends on some fundamental knowledge of modal logic have always been important in philosophy of religion, metaphysics, and epistemology. Moreover, modal logic has become increasingly important with the use of the concept of "possible worlds" in these areas. Introductory Modal Logic fills the need for a basic text on modal logic, accessible to students of elementary symbolic logic. Kenneth Konyndyk presents a natural deduction treatment of propositional modal logic and quantified modal logic, historical information about its development, and discussions of the philosophical issues raised by modal logic. Characterized by clear and concrete explanations, appropriate examples, and varied and challenging exercises, Introductory Modal Logic makes both modal logic and the possible-worlds metaphysics readily available to the introductory level student.

This 1995 book argues that a proper understanding of Aristotle's modal logic requires an appreciation of its connection to the metaphysics.